Paper Authors

Wayne Padgett
Rose-Hulman Institute of Technology

Wayne T. Padgett received his Ph.D. from Georgia Institute of Technology in 1994. He has been teaching digital signal processing and related courses at Rose-Hulman Institute of Technology for 12 years. He is a member of ASEE, a senior member of the IEEE, and is on the IEEE Signal Processing Society’s Technical Committee on Signal Processing Education.

Abstract

NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

In this paper a description of a unique fixed point systems course, including a list of topics, a
description of labs, and a discussion of the focus on a course project. The course has run four
times using simulation environments to promote analysis and visualization. The content of the
course has made it apparent that there are numerous linkages to advanced signal processing
topics, and these are described. The course has also led to the initiation of an educational
experiment using the Signals and Systems Concept Inventory (SSCI) to measure how two very
different electives affect student understanding of basic concepts. The experiment compares the
fixed point course which is very lab oriented, to a theoretical elective. Preliminary results are
described. Work to develop a course text and lab materials is described as part of an effort to
promote the adoption of fixed point material widely in electrical and computer engineering
curricula.

Introduction

Fixed-point implementation issues in digital signal processing (DSP) are not widely taught or
deeply covered in most U.S. undergraduate (or graduate) curricula. There seems to be a
perception among faculty that fixed-point implementation is difficult to tie to theory, and not
important for advanced work in the field. However, the author’s experiences show that industrial
practitioners rely heavily on fixed-point implementation skills, and that many opportunities exist
to link a fixed-point implementation course to advanced signal processing topics. The author has
taught a fixed-point system design course four times, and each time the need to draw on
advanced topics has become more obvious.

Course Description

The course is called DSP System Design, not Fixed-Point Algorithm Development, because the
only way to give students adequate experience with the tradeoffs and performance issues
involved is to build the course around a project. Learning to measure, specify, and adjust the
system’s performance is a critical element of the course, and it drives the students to deepen their
understanding of the fixed-point effects. Although many possible projects could serve well, the
course has been based on an SSB communication system which takes input speech at an 8 kHz
sample rate and then raises the sample rate to 96 kHz (12x) for SSB modulation at 40 kHz
(actually four channels are implemented eventually). The receiver removes out of band
interference, demodulates the signal, and then reduces the sample rate back to 8 kHz. The basic
design is then extended to operate at four channel frequencies with minimal inter-channel
interference, and subject to various (conflicting) performance criteria such as speech quality,
SNR, and computational complexity.

In the past three offerings, all of the course project work has been done in MATLAB, primarily
using the Fixed Point Toolbox functions. All of the fixed-point system development is done as